Income Taxes - Federal and State Net Operating Loss and Tax Credit Carryovers (Details) $ in Millions	Dec. 31, 2019 USD ($)
U.S.
Operating Loss Carryforwards [Line Items]
Net operating loss carryover	$ 1,484
U.S. | 2035 - 2037
Operating Loss Carryforwards [Line Items]
Net operating loss carryover	1,056
U.S. | No Expiration
Operating Loss Carryforwards [Line Items]
Net operating loss carryover	428
State | 2029 - 2038
Operating Loss Carryforwards [Line Items]
Net operating loss carryover	$ 227